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TRF7970A: Select command doesn't return SAK. Select then NFC Type 2 Read doesn't work.

Part Number: TRF7970A
Other Parts Discussed in Thread: MSP-EXP430G2ET, DLP-7970ABP

Hello,

I'm using the DLP-RFID2, which references this firmware design guide:

www.ti.com/.../sloa157.pdf

I'm attempting to read from a 14443-A tag.

First, I send the A0 REQA command which returns the tag's UID and SSI.

Then I send the A2 SELECT command with the discovered UID. This command doesn't seem to return the SAK, or anything for that matter. This might be pertain to this forum response that I found: 

https://e2e.ti.com/support/wireless-connectivity/other-wireless/f/667/t/552766

If I then try an NFC Type 2 Read, I don't get anything back.

However, if I send the A0 REQA and follow that up with a Type 2 Read, I can successfully read from the tag.

My questions are as follows:

1) Does the SELECT command do anything? If not, is there a way to get it to do something?

2) Can the REQA command find more than two tags simultaneously?

Thanks,

Max

  • Hello Max,

    Max Kross2 said:
    1) Does the SELECT command do anything? If not, is there a way to get it to do something?

    No, as I stated in that past post:

    I never developed any of the TRF7970AEVM firmware, so I wasn't aware of how it seems to be setup. I'm not entirely sure what the purpose of that 0xA2 select command is to be honest. I went through the firmware flow, and it makes no logical sense, as it doesn't appear to do anything... so then I also used a TRF7970AEVM +GUI and sniffed the over the air communication, and basically confirmed that the Select command there does not do anything productive. Why it exists is a mystery to me right now...

    Max Kross2 said:
    2) Can the REQA command find more than two tags simultaneously?

    No, you would do that with the anti-collision process, not REQA.

    I never tested the anti-collision for that code in detail but I wouldn't be surprised if it cannot support multiple tags.

    I would recommend getting our DLP-7970ABP and an MSP-EXP430G2ET and use our http://ti.com/lit/zip/sloc297 firmware which has a better architected anti-collision process.